Plasma processing apparatus and plasma processing method

ABSTRACT

A plasma processing apparatus includes: a chamber; first and second matching circuits; a first RF generator generating a first RF pulsed signal including a plurality of first pulse cycles in which each cycle includes first, second, and third periods, and the first RF pulsed signal has first, second, and third power levels in first, second, and third periods, respectively; a second RF generator generating a second RF pulsed signal including a plurality of second pulse cycles in which each cycle includes fourth and fifth periods, and the second RF pulsed signal has fourth and fifth power levels in fourth and fifth periods, respectively; and a third RF generator generating a third RF pulsed signal including a plurality of third pulse cycles in which each cycle includes sixth and seventh periods, and the third RF pulsed signal has sixth and seventh power levels in sixth and seventh periods, respectively.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 17/475,909, filed on Sep. 15, 2021, which claimspriority from Japanese Patent Application No. 2020-154843, filed on Sep.15, 2020, with the Japan Patent Office, all of which are incorporatedherein in their entireties by reference.

TECHNICAL FIELD

The present disclosure relates to a plasma processing apparatus and aplasma processing method.

BACKGROUND

Japanese Patent Laid-Open Publication No. 2019-067503 proposes, forexample, an inductively coupled plasma (ICP) apparatus that includes tworadio-frequency power supplies to supply radio-frequency powers of twofrequencies to an antenna above a chamber and a lower electrode(susceptor). Of the two radio-frequency power supplies, oneradio-frequency power supply supplies a bias radio-frequency powerhaving a frequency of, for example, 13 MHz to the lower electrode. Theantenna is provided above the chamber, and the other radio-frequencypower supply supplies a plasma excitation radio-frequency power of afrequency of, for example, 27 MHz to the central point of the lineconstituting an outer coil of the antenna, or the vicinity thereof.

SUMMARY

According to an aspect of the present disclosure, a plasma processingapparatus includes: a chamber; a first matching circuit coupled to thechamber; a second matching circuit coupled to the chamber; a first RFgenerator coupled to the first matching circuit, and configured togenerate a first RF pulsed signal including a plurality of first pulsecycles, each first pulse cycle including a first period, a secondperiod, and a third period, and the first RF pulsed signal having afirst power level in the first period, a second power level in thesecond period, and a third power level in the third period; a second RFgenerator coupled to the second matching circuit, and configured togenerate a second RF pulsed signal including a plurality of second pulsecycles, each second RF pulse cycle including a fourth period and a fifthperiod, the second RF pulsed signal having a frequency lower than afrequency of the first RF pulsed signal and having a fourth power levelin the fourth period and a fifth power level in the fifth period, andthe fourth period being set not to overlap with the first period; and athird RF generator coupled to the second matching circuit, andconfigured to generate a third RF pulsed signal including a plurality ofthird pulse cycles, each third pulse cycle including a sixth period anda seventh period, the third RF pulsed signal having a frequency lowerthan the frequency of the second RF pulsed signal and having a sixthpower level in the sixth period and a seventh power level in the seventhperiod, and the sixth period being set not to overlap with the firstperiod and the fourth period.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the drawings and the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view illustrating an example of aplasma processing system according to an embodiment.

FIG. 2 is a view illustrating an example of a plasma processingapparatus according to an embodiment.

FIG. 3 is a view illustrating an example of a matching circuit of twobias RF pulsed signals according to an embodiment.

FIG. 4 is a view illustrating examples of radicals, ions, an electrontemperature, an ion energy, and by-products.

FIG. 5 is a view illustrating pulse patterns of radio-frequency powerpulses of two frequencies according to an embodiment.

FIG. 6 is a view illustrating pulse patterns of radio-frequency powerpulses of three frequencies according to an embodiment.

FIG. 7 is a view illustrating pulse patterns of radio-frequency powerpulses of three frequencies according to an embodiment.

FIG. 8 is a view illustrating pulse patterns of radio-frequency powerpulses of three frequencies according to an embodiment.

FIG. 9 is a view illustrating pulse patterns of radio-frequency powerpulses of three frequencies according to an embodiment.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof. The illustrativeembodiments described in the detailed description, drawings, and claimsare not meant to be limiting. Other embodiments may be utilized, andother changes may be made without departing from the spirit or scope ofthe subject matter presented here.

Hereinafter, embodiments for implementing the present disclosure will bedescribed with reference to the drawings. In the respective drawings,the same components will be denoted by the same reference numerals, andoverlapping descriptions thereof may be appropriately omitted.

[Plasma Processing System]

First, a plasma processing system according to an embodiment will bedescribed with reference to FIGS. 1 and 2 . FIG. 1 is a schematiccross-sectional view illustrating an example of the plasma processingsystem according to the embodiment. FIG. 2 is a view illustrating anexample of a plasma processing apparatus 1 according to an embodiment.

In an embodiment, the plasma processing system includes the plasmaprocessing apparatus 1 and a controller 2. The plasma processingapparatus 1 is configured to supply three radio-frequency power pulses(three RF pulsed signals) into a chamber 10, thereby generating plasmafrom a processing gas in the chamber 10. The plasma processing apparatus1 may be configured to supply two radio-frequency power pulses (two RFpulsed signals) into the chamber 10, thereby generating plasma from theprocessing gas in the chamber 10. Then, the plasma processing apparatus1 exposes the generated plasma to a substrate so as to process thesubstrate.

The plasma processing apparatus 1 includes a chamber 10, a substratesupport 11, and a plasma generator. The chamber 10 defines a plasmaprocessing space 10 s. Further, the chamber 10 includes a gas inlet 10 afor supplying at least one processing gas into the plasma processingspace 10 s, and a gas outlet 10 b for discharging the gas from theplasma processing space. The gas inlet 10 a is connected to at least onegas supply 20.

The gas outlet 10 b is, for example, an exhaust port provided at thebottom of the chamber 10, and is connected to an exhaust system 40. Theexhaust system 40 may include a pressure valve and a vacuum pump. Thevacuum pump may include a turbo molecular pump, a roughing pump, or acombination thereof.

The substrate support 11 is disposed in the plasma processing space 10 sto support a substrate W. The plasma generator is configured to generateplasma from at least one processing gas supplied into the plasmaprocessing space 10 s. The plasma formed in the plasma processing space10 s may be capacitively coupled plasma (CCP) or inductively coupledplasma (ICP).

The controller 2 processes computer-executable instructions forinstructing the plasma processing apparatus 1 to execute variousprocesses to be described herein below. The controller 2 may beconfigured to control the respective components of the plasma processingapparatus 1 to execute the various processes to be described hereinbelow. In an embodiment, as illustrated in FIG. 1 , a portion of thecontroller 2 or the entire controller 2 may be included in the plasmaprocessing apparatus 1. The controller 2 may include, for example, acomputer 21. The computer 21 may include, for example, a processing unit(central processing unit (CPU)) 21 a, a storage unit 21 b, and acommunication interface 21 c. The processing unit 21 a may be configuredto perform various control operations based on programs stored in thestorage unit 21 b. The storage unit 21 b may include a random accessmemory (RAM), a read only memory (ROM), a hard disk drive (HDD), a solidstate drive (SSD), or a combination thereof. The communication interface21 c may communicate with the plasma processing apparatus 1 through acommunication line such as a local area network (LAN).

Hereinafter, an example of a configuration of the plasma processingapparatus 1 will be further described, using the inductively coupledplasma processing apparatus of FIG. 2 as an example. The plasmaprocessing apparatus 1 includes the chamber 10. The chamber 10 includesa dielectric window 10 c and a side wall 10 d. The dielectric window 10c and the side wall 10 d define the plasma processing space 10 s in thechamber 10. Further, the plasma processing apparatus 1 includes thesubstrate support 11, a gas introduction unit 13, the gas supply 20, apower supply, and the antenna 14.

The substrate support 11 is disposed in the plasma processing space 10 sinside the chamber 10. The antenna 14 is disposed on or above thechamber 10 (the dielectric window 10 c).

The substrate support 11 includes a main body and an annular member (anedge ring) 12. The main body has a central region (a substrate supportsurface) 11 a for supporting the substrate (wafer) W, and an annularregion (an edge ring support surface) 11 b for supporting the annularmember 12. The annular region 11 b of the main body surrounds thecentral region 11 a of the main body. The substrate W is placed on thecentral region 11 a of the main body, and the annular member 12 isdisposed on the annular region 11 b of the main body to surround thesubstrate W on the central region 11 a of the main body. In theembodiment, the main body includes an electrostatic chuck 111 and aconductive member 112. The electrostatic chuck 111 is disposed on theconductive member 112. The conductive member 112 functions as an RFelectrode, and the upper surface of the electrostatic chuck 111functions as a substrate supporting surface (the central region 11 a).Although not illustrated, in an embodiment, the substrate support 11 mayinclude a temperature control module configured to adjust at least oneof the electrostatic chuck 111 and the substrate W to a targettemperature. The temperature control module may include a heater, a flowpath, or a combination thereof. A temperature control fluid such as arefrigerant or a heat transfer gas flows through the flow path. Thechamber 10, the substrate support 11, and the annular member 12 arearranged to coincide with each other around the central axis Z.

The gas introduction unit 13 is configured to supply at least oneprocessing gas from the gas supply 20 into the plasma processing space10 s. In the embodiment, the gas introduction unit 13 is disposed abovethe substrate support 11, and attached to the central opening formed inthe dielectric window 10 c.

The gas supply 20 may include at least one gas source 23 and at leastone flow rate controller 22. In the embodiment, the gas supply 20 isconfigured to supply one or more processing gases from the respectivecorresponding gas sources 23 to the gas introduction unit 13 via therespective corresponding flow rate controllers 22. Each flow ratecontroller 22 may include, for example, a mass flow controller or apressure-controlled flow rate controller. Further, the gas supply 20 mayinclude one or more flow rate modulation devices that modulate or pulseflow rates of one or more processing gases.

The power supply includes an RF power supply 31 coupled to the chamber10. The RF power supply 31 is configured to supply three RF signals (RFpowers) to the conductive member 112 of the substrate support 11 or theantenna 14. As a result, plasma is formed from at least one processinggas supplied into the plasma processing space 10 s. The plasma generatormay include the gas supply 20 that supplies at least one processing gasinto the plasma processing space 10 s, and the RF power supply 31, andmay be configured to generate plasma from the processing gas.

The antenna 14 includes one or more coils. In an embodiment, the antenna14 may include an outer coil and an inner coil that are coaxiallyarranged. In this case, the RF power supply 31 may be connected to boththe outer coil and the inner coil, or may be connected to either theouter coil or the inner coil. In the former case, the same RF generatormay be connected to both the outer coil and the inner coil, or separateRF generators may be connected to the outer coil and the inner coil,respectively.

In the embodiment, the RF power supply 31 includes a source RF generator31 a, a first bias RF generator 31 b, and a second bias RF generator 31c. The source RF generator 31 a is connected to the antenna 14, and thefirst bias RF generator 31 b and the second bias RF generator 31 c arecoupled to the conductive member 112. The source RF generator 31 a iscoupled to the antenna 14 via a first matching circuit 33, andconfigured to generate a first RF pulsed signal (hereinafter, alsoreferred to as an HF power) for generating plasma. In an embodiment, thefirst RF pulsed signal has a frequency in a range of 20 MHz to 60 MHz.The generated first RF pulsed signal is supplied to the antenna 14. Thefirst RF pulsed signal includes a plurality of first pulse cycles, andeach of the plurality of first pulse cycles first, second, and thirdperiods. The first RF pulsed signal has a first power level in the firstperiod, a second power level in the second period, and a third powerlevel in the third period. The first RF pulsed signal has at least threepower levels, each of which is zero (0) or more. Accordingly, the firstRF pulsed signal may have High/Middle/Low power levels, which are largerthan zero (0). Further, the first RF pulsed signal may have High/Lowpower levels and a zero (0) power level (OFF). The source RF generator31 a is an example of a first RF generator coupled to the first matchingcircuit 33 and configured to generate the first RF pulsed signal thatincludes the plurality of first pulse cycles.

Further, the first bias RF generator is connected to the conductivemember 112 of the substrate support 11 via a second matching circuit 34and a power feeding line 37, and configured to generate a second RFpulsed signal (hereinafter, also referred to as an LF1 power). Thegenerated second RF pulsed signal is supplied to the conductive member112 of the substrate support 11. In an embodiment, the second RF pulsedsignal has a frequency lower than the frequency of the first RF pulsedsignal. In an embodiment, the second RF pulsed signal has a frequency ina range of 1 MHz to 15 MHz. The second RF pulsed signal has a fourthpower level in a fourth period, and a fifth power level in a fifthperiod. The fourth period is 30 μs or less. Accordingly, the second RFpulsed signal may have High/Low power levels, which are zero (0) ormore. Further, the second RF pulsed signal may have a power level morethan zero (0) and a zero (0) power level, that is, ON/OFF signals. Thefirst bias RF generator is an example of a second RF generator coupledto the second matching circuit 34 and configured to generate the secondRF pulsed signal that include a plurality of second pulse cycles.

Further, the second bias RF generator is connected to the conductivemember 112 of the substrate support 11 via the second matching circuit34 and the power feeding line 37, and configured to generate a third RFpulsed signal (hereinafter, also referred to as an LF2 power). Thegenerated third RF pulsed signal is supplied to the conductive member112 of the substrate support 11. In an embodiment, the third RF pulsedsignal has a frequency lower than the frequency of the second RF pulsedsignal. In an embodiment, the third RF pulsed signal has a frequency ina range of 100 kHz to 4 MHz. The third RF pulsed signal has a sixthpower level in a sixth period, and a seventh power level in a seventhperiod. The third RF pulsed signal has at least two power levels, eachof which is zero (0) or more. Accordingly, the third RF pulsed signalmay have High/Low power levels, which are zero (0) or more. Further, thethird RF pulsed signal may have a power level more than zero (0) and azero (0) power level, that is, ON/OFF signals. The second bias RFgenerator is an example of a third RF generator coupled to the secondmatching circuit 34, and configured to generate the third RF pulsedsignal that includes a plurality of third pulse cycles.

In this way, the first RF pulsed signal, the second RF pulsed signal,and the third RF pulsed signal are pulsed. The second RF pulsed signaland the third RF pulsed signal are pulsed between the ON state and theOFF state or between the two or more different ON states (High/Low). Thefirst RF pulsed signal is pulsed among the two or more different ONstates (High/Low) and the OFF state, or among the three or moredifferent ON states (High/Middle/Low). The first RF pulsed signal may bepulsed between the ON state and the OFF state, or between two differentON states (High/Low).

The first matching circuit 33 is connected to the source RF generator 31a and the antenna 14, and connected to the chamber 10 via the antenna14. The first matching circuit 33 enables the first RF pulsed signal tobe supplied from the source RF generator 31 a to the antenna 14 via thefirst matching circuit 33. Further, the first matching circuit 33 may beconnected to a component other than the antenna 14 in another plasmaprocessing apparatus. For example, in a capacitively coupled plasmaprocessing apparatus that includes two opposing electrodes, the firstmatching circuit 33 may be connected to one of the two electrodes.

The second matching circuit 34 is connected to the first bias RFgenerator 31 b, the second bias RF generator 31 c, and the substratesupport 11 (the conductive member 112). The second matching circuit 34enables the second RF pulsed signal to be supplied from the first biasRF generator 31 b to the substrate support 11 via the second matchingcircuit 34. Further, the second matching circuit 34 enables the third RFpulsed signal to be supplied from the second bias RF generator 31 c tothe substrate support 11 via the second matching circuit 34.

The controller 2 outputs a control signal for instructing to supply eachpulsed signal to each of the source RF generator 31 a, the first bias RFgenerator 31 b, and the second bias RF generator 31 c. Accordingly, thefirst RF pulsed signal, the second RF pulsed signal, and the third RFpulsed signal each of which includes a plurality of pulse cycles aresupplied at predetermined timings, and plasma is generated from theprocessing gas in the chamber 10. Then, the generated plasma is exposedto the substrate, so as to perform a substrate processing. As a result,the efficiency of the process may be improved, and thus, the substrateprocessing may be implemented with a high accuracy. The timings when thecontroller 2 controls the ON/OFF states of the first RF pulsed signal,the second RF pulsed signal, and the third RF pulsed signal, or thepower levels that are zero (0) or more will be described later.

Example of Internal Configuration of Second Matching Circuit

Next, an example of the configuration of the second matching circuit 34will be described with reference to FIG. 3 . FIG. 3 is a viewillustrating an example of the internal configuration of the secondmatching circuit 34 according to an embodiment.

The first bias RF generator 31 b and the second bias RF generator 31 care connected to the substrate support 11 (the conductive member 112)via the second matching circuit 34 and the power feeding line 37. Thesecond RF pulsed signal supplied from the first bias RF generator 31 bwill also be referred to as the LF1 power in the following descriptions.Further, the third RF pulsed signal supplied from the second bias RFgenerator 31 c will also be referred to as the LF2 power in thefollowing descriptions.

When the second RF pulsed signal (the LF1 power) supplied from the firstbias RF generator 31 b is coupled to the opposite side (the second biasRF generator 31 c) via the power feeding line 36 in the second matchingcircuit 34, the supply efficiency of the LF1 power supplied to thechamber 10 is deteriorated. Similarly, when the third RF pulsed signal(the LF2 power) supplied from the second bias RF generator 31 c iscoupled to the opposite side (the first bias RF generator 31 b) via thepower feeding line 36, the supply efficiency of the LF2 power suppliedto the chamber 10 is deteriorated. Then, since the supply of the biaspower to the chamber 10 is reduced, it becomes difficult to control theion energy or the like, and the process performance is deteriorated.

Thus, the second matching circuit 34 according to the present embodimentincludes a first adjustment circuit 34 b 1, a first separation circuit34 b 2, a second adjustment circuit 34 c 1, and a second separationcircuit 34 c 2. The first adjustment circuit 34 b 1 and the firstseparation circuit 34 b 2 are connected between the first bias RFgenerator 31 b and the power feeding line 37. The second adjustmentcircuit 34 c 1 and the second separation circuit 34 c 2 are connectedbetween the second bias RF generator 31 c and the power feeding line 37.With this configuration, the second RF pulsed signal (the LF1 power)generated in the first bias RF generator 31 b is supplied to thesubstrate support 11 (the conductive member 112), while being suppressedfrom being coupled to the second bias RF generator 31 c. Further, thethird RF pulsed signal (the LF2 power) generated in the second bias RFgenerator 31 c is supplied to the substrate support 11 (the conductivemember 112), while being suppressed from being coupled to the first biasRF generator 31 b.

The first adjustment circuit 34 b 1 includes a variable element, and isconfigured to match the impedance of the load side (the substratesupport 11) of the first bias RF generator 31 b with the outputimpedance of the first bias RF generator 31 b. In an embodiment, thevariable element of the first adjustment circuit 34 b 1 is a variablecapacitor.

The second separation circuit 34 c 2 is connected between the secondbias RF generator 31 c and the substrate support 11, and suppresses thecoupling of the second RF pulsed signal which is the LF1 power from thefirst bias RF generator 31 b.

The second adjustment circuit 34 c 1 includes a variable element, and isconfigured to match the impedance of the load side (the substratesupport 11) of the second bias RF generator 31 c with the outputimpedance of the second bias RF generator 31 c. In an embodiment, thevariable element of the second adjustment circuit 34 c 1 is a variableinductor.

The first separation circuit 34 b 2 is connected between the first biasRF generator 31 b and the substrate support 11, and suppresses thecoupling of the third RF pulsed signal which is the LF2 power from thesecond bias RF generator 31 c.

The second separation circuit 34 c 2 is an RF choke circuit thatincludes an inductor L2. The first separation circuit 34 b 2 is aresonant circuit that includes a capacitor C1 and an inductor L1. Thefirst separation circuit 34 b 2 is configured by the capacitor C1 andthe inductor L1. The second separation circuit 34 c 2 is configured bythe inductor L2.

The first separation circuit 34 b 2 sets circuit constants of C1 and L1such that the impedance viewed from the second RF pulsed signal seems tobe zero (0) or close to zero (0), and the impedance viewed from thethird RF pulsed signal seems to be high and seems to be a wall close tothe first bias RF generator 31 b. Then, when the impedance of the firstseparation circuit 34 b 2 viewed from the third RF pulsed signal isZ_(LF2), and the load impedance of the plasma is Z_(chamber),Z_(LF2)>>Z_(chamber) is established.

Further, the second separation circuit 34 c 2 sets a circuit constant ofL2 such that the impedance viewed from the third RF pulsed signal seemsto be zero (0) or close to zero (0), and the impedance viewed from thesecond RF pulsed signal seems to be high and seems to be a wall close tothe second bias RF generator 31 c. Then, when the impedance of thesecond separation circuit 34 c 2 viewed from the second RF pulsed signalis Z_(LF1), Z_(LF1)>>Z_(chamber) is established.

By setting the circuit constants of the first separation circuit 34 b 2as described above, the impedance Z_(LF2) of the first separationcircuit 34 b 2 becomes much larger than the load impedance Z_(chamber)of the plasma. Accordingly, the first separation circuit 34 b 2suppresses the coupling of the third RF pulsed signal from the secondbias RF generator 31 c (“LF2 Power→A” in FIG. 3 ). As a result, the LF2power is supplied into the chamber 10 through the power feeding line 37,so that the deterioration of the supply efficiency of the LF2 power maybe suppressed.

Similarly, by setting the circuit constant of the second separationcircuit 34 c 2 as described above, the impedance Z_(LF1) of the secondseparation circuit 34 c 2 becomes much larger than the load impedanceZ_(chamber) of the plasma. Accordingly, the second separation circuit 34c 2 suppresses the coupling of the second RF pulsed signal from thefirst bias RF generator 31 b (“LF1 Power→A” in FIG. 3 ). As a result,the LF1 power is supplied into the chamber 10 through the power feedingline 37, so that the deterioration of the supply efficiency of the LF1power may be suppressed.

With this configuration, the pulsed signals of the two bias powers (theLF1 power and the LF2 power) having different frequencies may beefficiently supplied to the substrate support 11.

[Pulsed Signals]

For example, in a process of etching a deep hole having a high aspectratio, the incidence angle of ions may be made vertical, or the maskselectivity may be increased, by using the pulsed signals of the HFpower, the LF1 power, and the LF2 power.

FIG. 4 is a view illustrating examples of radicals, ions, an electrontemperature, an ion energy, and by-products. The horizontal axis of FIG.4 represents the time that elapses after the supply of the RF power isstopped (OFF) (one cycle). The vertical axis of FIG. 4 represents thestates of the radicals (Radical), the ions (Ions), the electrontemperature (Te), the ion energy (ϵ_(I)), and the by-products(By-products) in each time from the OFF time.

According to the states, while the variation of the radicals (Radical)after the OFF state of the RF power is slow, the variations of the ions(Ions) and the plasma temperature (Te) after the OFF state of the RFpower are faster than the variation of the radicals. The pulsed signalsof the HF power and the LF power (e.g., the LF1 power and the LF2 power)are controlled in consideration of, for example, the attenuation ofradicals or ions in plasma or the variation of energy. As for an exampleof the pulsed signal of the LF power supplied after the HF power isturned OFF, a control may be considered which turns OFF the LF powerduring the initial time when the plasma temperature (Te) is high, andturns ON the LF power after the plasma temperature (Te) decreases. As aresult, the ions may be effectively drawn into the substrate, using theLF power in the time when the ions still remain, but the plasmatemperature (Te) is low.

As for another example of the pulsed signal of the LF power suppliedafter the HF power is turned OFF, the LF2 power may be controlled, byusing ϵ_(I) that indicates the ion energy as a plasma parameter, duringthe time when the plasma electron temperature (Te) does notsubstantially vary. As a result, by controlling the ion energy (ϵ_(I)),the incidence angle of ions may be controlled to be more vertical.

In this way, the timings for turning ON/OFF the HF power and the LFpower are finely controlled according to the movements of the plasmaparameters such as the radicals, the ions, the plasma electrontemperature, the ion energy, and the by-products. As a result, theperformance of the process may be improved. Hereinafter, the timings forsupplying the pulsed signals of the radio-frequency powers will bedescribed with reference to FIGS. 5 to 8 . The timings for supplying thepulsed signals of the radio-frequency powers are controlled by thecontroller 2.

(Pulsed Signals of Two Frequencies)

FIG. 5 is a view illustrating pulse patterns of radio-frequency powerpulses of two frequencies according to an embodiment. Of theradio-frequency power pulses of two frequencies illustrated in FIG. 5 ,the HF power (Source Power) includes a plurality of first pulse cycles.The pulsed signal of the LF1 power (Bias Power) includes a plurality ofsecond pulse cycles. Hereinafter, the timings for supplying therespective pulsed signals will be described. In FIG. 5 , the horizontalaxis represents the time of one cycle, and the vertical axis representsthe ON/OFF states of the HF power and the LF1 power. Each of theplurality of first pulse cycles of the HF power includes periods (1) and(2), and each of the plurality of second pulse cycles of the LF1 powerincludes periods (3) and (4). In the example of FIG. 5 , the first RFpulsed signal of the HF power is repeated per cycle that includes theperiods (1) and (2) of each of the plurality of first pulse cycles, andan exhaust period. The second RF pulsed signal of the LF1 power isrepeated per cycle that includes the periods (4) and (3) of each of theplurality of second pulse cycles, and an exhaust period.

The source RF generator 31 a is configured to generate the first RFpulsed signal (the HF power). In the present embodiment, the first RFpulsed signal has the two power levels (ON/OFF). The first bias RFgenerator 31 b is configured to generate the second RF pulsed signal(the LF1 power). In the present embodiment, the second RF pulsed signalhas the two power levels (ON/OFF).

The ON state of the HF power and the ON state of the LF1 power do notoverlap with each other in time. For example, the first RF pulsed signalhas the first power level in the period (1) and the second power levelin the period (2), in which the first power level is the ON state, andthe second power level is the OFF state. That is, the second power levelis the zero (0) power level. The second RF pulsed signal has the thirdpower level in the period (3) and the fourth power level in the period(4), in which the third power level is the ON state, and the fourthpower level is the OFF state. That is, the fourth power level is thezero (0) power level.

The first RF pulsed signal may have a frequency of 27 MHz. The frequencyof the second RF pulsed signal is lower than the frequency of the firstRF pulsed signal. For example, the second RF pulsed signal has afrequency of 13 MHz. The first power level may be High, and the secondpower level may be Low. Further, the third power level may be High, andthe fourth power level may be Low.

In FIG. 5 , the HF power is maintained in the ON state in the period(1), and the LF1 power is maintained in the OFF state in the period (4)that coincides with the period (1) in time. Accordingly, in the timefrom a timing t₀ to a timing t₁, plasma containing radicals and ions isgenerated by the supply of the HF power.

At the timing t₁, the HF power shifts to the OFF state, the LF1 powershifts to the ON state, the HF power is maintained in the OFF state inthe period (2), and the LF1 power is maintained in the ON state in theperiod (3) that coincides with the period (2) in time. Since the HFpower is in the OFF state in the period (2), the radicals, the ions, andthe plasma temperature are attenuated with their respective timeconstants, as in the example illustrated in FIG. 4 . The flux of ions(the amount of ions) that reach the bottom of a recess being etched iscontrolled by the supply of the LF1 power in the period (3), so that theetching is promoted. At a timing t₂, the HF power is maintained in theOFF state, and the LF1 power shifts to the OFF state. Since the HF powerand the LF1 power are in the OFF state in the exhaust period after theperiods (2) and (3), the by-products are exhausted. Each exhaust periodis preset to a time during which the by-products do not adhere to thesubstrate W.

One cycle ends at a timing t₃ after the exhaust period, and shifts tothe period (1) of the next cycle. Then, the HF power shifts to the ONstate again at the time to of the next cycle, and the LF1 power ismaintained in the OFF state in the period (4). That is, the first pulsecycle of the HF power is repeated per cycle that includes the periods(1) and (2), and the exhaust period. Further, the second pulse cycle ofthe LF1 power is repeated per cycle that includes the periods (4) and(3), and the exhaust period. One cycle is 1 kHz to 20 kHz. The pluralityof pulse cycles have the same time period, and each pulse cycle has atime period of 50 μs to 1,000 μs. That is, one cycle of the pulse cycleis 50 μs to 1,000 μs.

The period (3) does not overlap with the period (1) in time. That is,the first bias RF generator 31 b offsets the timing for changing thepower level of the second RF pulsed signal with respect to the timingfor changing the power level of the first RF pulsed signal, such thatthe ON state of the HF power and the ON state of the LF1 power do notoverlap with each other in time.

The period (3) is set to 30 μs or less. The periods (1), (2), and (4)are set to arbitrary time, and may be longer than 30 μs. That is, in thepresent example, ON/OFF of the LF1 power is repeated in the manner thatthe LF1 power is maintained in the ON state for the time of 30 μs orless in the period (3), and maintained in the OFF state for arbitrarytime in the period (4) and the exhaust period. In this way, when thesupply time of the LF1 power in one cycle is set to 30 μs or less, theincidence angle of ions is controlled to be vertical, so that an etchingwith a high anisotropy may be implemented.

The power level of the HF power in the period (1) is an example of thefirst power level, and the power level of the HF power in the period (2)is an example of the second power level. The power level of the LF1power in the period (3) is an example of the third power level, and thepower level of the LF1 power in the period (4) is an example of thefourth power level.

(Pulsed Signals of Three Frequencies)

FIGS. 6 to 8 are views illustrating pulse patterns of radio-frequencypower pulses of three frequencies according to an embodiment. The pulsedsignal of each of the HF power (Source Power), the LF1 power (Bias1Power), and the LF2 power (Bias2 Power), which are the radio-frequencypowers of the three frequencies illustrated in FIGS. 6 to 8 , includes aplurality of pulse cycles. Hereinafter, the timings for supplying eachpulsed signal will be described. In FIGS. 6 to 8 , the horizontal axisrepresents the time of one cycle, and the vertical axis represents theON/OFF states of the HF power, the LF1 power, and the LF2 power. Thecontrol of the pulsed signal of each of the HF power, the LF1 power, andthe LF2 power is repeated per cycle that includes the first pulse cycleof the HF power, the second pulse cycle of the LF1 power, or the thirdpulse cycle of the LF2 power (All of the pulse cycles each include theexhaust period).

In the control of the radio-frequency power pulses of the threefrequencies, the ON state of the LF1 power and the ON state of the LF2power do not overlap with each other in time, in the manner that the LF2power is turned OFF while the LF1 power is turned ON, and the LF2 poweris turned ON while the LF1 power is turned OFF. Further, the High powerlevel of the HF power and the ON state of the LF1 power do not overlapwith each other in time, in the manner that the LF1 power is turned OFFwhile the HF power is set to the High power level, and the HF power isturned OFF or set to the Low power level while the LF1 power is turnedON. Similarly, the High power level of the HF power and the ON state ofthe LF2 power do not overlap with each other in time, in the manner thatthe LF2 power is turned OFF while the HF power is set to the High powerlevel, and the HF power is turned OFF or set to the Low power levelwhile the LF2 power is turned ON.

The source RF generator 31 a is configured to generate the first RFpulsed signal (the HF power), and in the present embodiment, the firstRF pulsed signal has the three power levels (High/Low/OFF). The powerlevels may be arbitrarily set and changed according to a target process.For example, the first RF pulsed signal has a frequency of 27 MHz.

The first bias RF generator 31 b is configured to generate the second RFpulsed signal (the LF1 power), and in the present embodiment, the secondRF pulsed signal has the two power levels (ON/OFF). That is, the secondRF pulsed signal has two or more power levels that include the zero (0)power level. The frequency of the second RF pulsed signal is lower thanthe frequency of the first RF pulsed signal. For example, the second RFpulsed signal has a frequency of 13 MHz.

The second bias RF generator 31 c is configured to generate the third RFpulsed signal (the LF2 power), and in the present embodiment, the thirdRF pulsed signal has the two power levels (ON/OFF). That is, the thirdRF pulsed signal has two or more power levels that includes the zero (0)power level. The frequency of the third RF pulsed signal is lower thanthe frequency of the second RF pulsed signal. For example, the third RFpulsed signal has a frequency of 1.2 MHz.

FIGS. 6 to 8 illustrate a state where the HF power is the first RFpulsed signal, the LF1 power is the second RF pulsed signal, and the LF2power is the third RF pulsed signal.

In the period (1) of FIG. 6 , the HF power has the High power level, andthe LF1 power and the LF2 power are turned OFF. That is, in the timefrom a timing to to a timing t₁₁, plasma containing radicals and ions isgenerated by the supply of the HF power. As a result, as illustrated in(a) of FIG. 6 , an etching target film 100 is etched through a mask 101,and the radicals R mainly adhere to the inner wall of the hole HL formedin the etching target film 100.

When the HF power shifts to the OFF state at a timing t₁₁ after theperiod (1) elapses, the radicals, the ions, and the plasma temperatureare attenuated with their respective time constants, as in the exampleillustrated in FIG. 4 . According to the attenuation state of the plasmaparameters, the timing for turning ON each of the LF1 power and the LF2power may be controlled in the period (3) when the HF power is turnedOFF, the period (2) when the power level is lowered, and the period whenthe by-products are exhausted. At this time, the period (4) when the LF1power is turned ON does not overlap, in time, with the period (1) whenthe HF power is set to the High power level. Further, a period (6) whenthe LF2 power is turned ON does not overlap with the periods (1) and (4)in time.

In the present embodiment, at the timing t₁₁, the HF power shifts fromthe High power level to the OFF state, and the LF1 power shifts to theON state. Accordingly, the LF1 power is maintained in the ON state inthe period (4) that coincides with the period (3) in time, and asillustrated in (b) of FIG. 6 , the flux of ions that reach the bottom ofthe etched recess may be controlled. Further, the amount of by-productsduring the etching may be suppressed. The LF2 power is maintained in theOFF state at the timing t₁₁, and maintained in the OFF state in a period(7) that coincides with the period (3) in time.

Further, the period (4) is set to time of 30 μs or less. Further, theperiod (4) does not overlap with the period (1) in time. When the LF1power is supplied for the short time of 30 μs or less in the period (4),the incidence angle of ions is controlled to be more vertical, so thatan etching with a high anisotropy may be implemented.

At a timing t₁₂ after the periods (3) and (4) elapse, the HF powershifts to the Low power level, the LF1 power shifts to the OFF state,and the LF2 power shifts to the ON state. In the period (2) until atiming t₁₃, the HF power is maintained at the Low power level. In theperiods (3) and (2), the HF power may be at the Low power level or maybe in the OFF state. The LF1 power is maintained in the OFF state in theperiod (5) that coincides with the period (2) in time, and the LF2 poweris maintained in the ON state in the period (6) that coincides with theperiod (2) in time. As described above, the period (6) does not overlapwith the periods (1) and (4) in time.

In the present embodiment, the LF2 power having a frequency lower thanthe frequency of the LF1 power supplied in the period (4) is supplied inthe period (6). The Vpp of the LF2 power is larger than the Vpp of theLF1 power. Accordingly, in the period (6), the Vpp of the bias voltagemay be made larger than that in the period (4), the ion energy ϵ_(I) maybe made further larger, and the incidence angle of ions may becontrolled to be more vertical. Thus, it is possible to control the fluxof ions that reach the bottom of the etched recess in the period (6)when the LF2 power is being supplied. As a result, as illustrated in (c)of FIG. 6 , a by-product B or the like that remains at, for example, thecorners of the bottom of the hole HL may be etched, so that the etchingmay be promoted.

In this way, in the process of etching a deep hole having a high aspectratio, the mask selectivity may be improved, and the incidence angle ofions may be made vertical, by using the pulsed signals of the HF power,the LF1 power, and the LF2 power. Thus, the etching shape may be madevertical, or the etching may be promoted. However, the process ofetching a deep hole having a high aspect ratio is an example of thesubstrate processing, and the type of the process is not limitedthereto.

In the exhaust period, the exhaust of by-products is controlled. Thatis, in the exhaust period, the HF power, the LF1 power, and the LF2power are controlled to be brought into the OFF state. Accordingly, asillustrated in (d) of FIG. 6 , the by-product B in the hole HL isexhausted. Then, the etching of the next cycle may be promoted. Theexhaust period is preset to time when the by-product B does not adhereto the substrate W again.

In the example of FIG. 6 , the power level of the HF power is controlledto the three levels, and the power levels of the LF1 power and the LF2power are controlled to the two levels of the ON/OFF states. However,the present disclosure is not limited thereto. For example, the powerlevel of the HF power may be controlled to four levels or more.

At a timing t₁₄, one cycle ends, and shifts to the period (1) of thenext cycle. Then, at a timing to of the next cycle, the HF power shiftsto the High power level, and the LF1 power and the LF2 power aremaintained in the OFF state. For the first RF pulsed signal, the HFpower is set to the predetermined state in the order of the period(1)→the period (3)→the period (2)→the exhaust period. For the second RFpulsed signal, the LF1 power is set to the predetermined state in theorder of the period (4)→the period (5)→the exhaust period. For the thirdRF pulsed signal, the LF2 power is set to the predetermined state in theorder of the period (7)→the period (6)→the exhaust period. Each pulsecycle is repeated, one cycle is 1 kHz to 20 kHz, and the period (4) is30 μs or less. The plurality of first to third pulse cycles have thesame time period, and each pulse cycle has a time period of 50 μs to1,000 μs. That is, one cycle of the pulse cycle is 50 μs to 1,000 μs.

The power level of the HF power in the period (1) is an example of thefirst power level, the power level of the HF power in the period (2) isan example of the second power level, and the power level of the HFpower in the period (3) is an example of the third power level. Thepower level of the LF1 power in the period (4) is an example of thefourth power level, and the power level of the LF1 power in the period(5) is an example of the fifth power level. The power level of the LF2power in the period (6) is an example of the sixth power level, and thepower level of the LF2 power in the period (7) is an example of theseventh power level.

FIG. 7 illustrates another example of the control of the radio-frequencypower pulses of the three frequencies. In this example as well, thecontrol of the pulsed signal of each of the HF power, the LF1 power, andthe LF2 power is repeated per cycle that includes the first pulse cycleof the HF power, the second pulse cycle of the LF1 power, or the thirdpulse cycle of the LF2 power. All of the pulse cycles may include theexhaust period.

The pulse cycle patterns of FIG. 6 and the pulse cycle patterns of FIG.7 are different from each other in that while FIG. 7 includes the delaytime T_(delay) after the timing t₁₁ at which the period (1) ends, FIG. 6does not include the delay time T_(delay) after the timing t₁₁. Thisdifference will be described hereafter, and descriptions of other pulsecycle patterns as illustrated in FIG. 8 will be omitted since the pulsecycle patterns are the same as illustrated in FIG. 6 .

For example, as illustrated in FIG. 4 , in a case where the LF1 power orthe LF2 power is turned ON when the plasma temperature (Te) is high, alarge amount of by-products are generated, which may hinder the etching.Accordingly, it may be conceivable to turn ON the LF1 power or the LF2power while avoiding the time when the plasma temperature is high. Thatis, the plasma temperature decreases at the timing t₂₁ after thepredetermined delay time T_(delay) elapses from the timing t₁₁. At thistiming, the LF1 power shifts to the ON state. That is, the LF1 powershifts to the ON state after time is shifted (delayed) by the delay timeT_(delay) from the timing t₁₁ when the HF power shifts to the OFF state.As a result, the amount of by-products during the etching may besuppressed, and the etching may be promoted.

In the present embodiment, the HF power is turned OFF in the delay timeT_(delay). However, the power level of the HF power in the delay timeT_(delay) may be set to the Low level which is lower than the powerlevel of the HF power in the period (1). By lowering the power level ofthe HF power, it is possible to reduce the generation of radicals andions in the delay time T_(delay) before the timing t₂₁ when the LF1power is supplied. As a result, it is possible to control the flux ofions that reach the bottom of the recess formed in the etching targetfilm in the period (4) from the timing t₂₁ to the timing t₁₂ after thedelay time T_(delay) elapses. The period (4) is set to a time of 30 μsor less. Further, the period (4) does not overlap with the period (1) intime. The next period (5) and the exhaust period are set to arbitrarytimes, and may be longer than 30 μs. In this way, when the LF1 power issupplied for the short time of 30 μs or less in the period (4), theincidence angle of ions is controlled to be more vertical, so that anetching with a high anisotropy may be implemented.

Further, at the timing t₁₂, the LF1 power shifts to the OFF state, andthe LF2 power shifts to the ON state. The LF1 power shifts to the OFFstate in the period (5), and the LF2 power shifts to the ON state in theperiod (6) that overlaps with the period (5) in time. Accordingly, inthe period (6), the incidence angle of ions may be controlled to be morevertical than that in the period (4). However, when the delay timeT_(delay) is excessively long, the ions are lost, and thus, the delaytime T_(delay) is preset to an appropriate value.

Through this control, the ON/OFF states of the LF1 power and the ON/OFFstates of the LF2 power are caused to shift to the ON state in differenttimes, so that the behavior of the ions is mainly controlled. The HFpower has the zero (0) power level in the period (3), the LF1 power hasa power level larger than zero (0) in the period (4), and the LF2 powerhas the zero (0) power level in the period (7) that overlaps with theperiod (4). The LF2 power has a power level larger than zero (0) in theperiod (6), the LF1 power has the zero (0) power level in the period (5)that overlaps with the period (6), and the HF power has a power levellarger than zero (0) in the period (2). That is, the times when the LF1power and the LF2 power have the power levels larger than zero (0) donot overlap with each other.

The LF2 power implements the mask selectivity higher than that of theLF1 power, and enables the vertical etching. In the period (1) when thepower level of the HF power is higher than that in the period (2), theradicals and the ions are generated in large amounts, and the effectsdescribed above may be hardly achieved even though the LF2 power issupplied in the period (1). Meanwhile, in the period (2) when the powerlevel of the HF power is lower than that in the period (1), and theperiod (3) of the zero (0) power level, the generation of radicals andions decreases. Accordingly, by supplying the LF1 power in the period(4) that overlaps with the period (3) and supplying the LF2 power in theperiod (6) that overlaps with the period (2), the effects describedabove may easily be achieved. Accordingly, by supplying the LF1 powerand the LF2 power in the periods, the ion energy may be increased, sothat the incidence angle of ions may be made vertical. As a result, inthe periods (2) and (3), the mask selectivity is higher than that in theperiod (1), and the vertical etching may be implemented.

Further, the LF1 power and the LF2 power may generate the pulsed signalsthat have the two power levels of the ON state and the OFF state.However, the LF1 power and the LF2 power may generate pulsed signalsthat have two or more power levels, such as the ON state, the OFF state,and the Middle power level. The LF1 power and the LF2 power may have twodifferent ON states.

FIG. 8 illustrates another example of the pulse patterns of theradio-frequency power pulses of the three frequencies. The control ofthe pulsed signal of each of the HF power, the LF1 power, and the LF2power is repeated per cycle that includes the first pulse cycle of theHF power, the second pulse cycle of the LF1 power, or the third pulsecycle of the LF2 power. All of the pulse cycles may include the exhaustperiod.

The pulse cycle patterns of FIG. 8 and the pulse cycle patterns of FIG.7 are different from each other, in that the order of turning ON the LF1power and the LF2 power in FIG. 8 is reverse to that in FIG. 7 , and thetiming of the delay time T_(delay) in FIG. 8 is shifted accordingly. Thedelay time T_(delay) is provided immediately before the LF1 power shiftsto the ON state.

In the present example as well, the LF1 power or the LF2 power is turnedON while avoiding the time when the plasma temperature is high. In thepresent example, the LF2 power and the LF1 power are turned ON in thisorder. At a timing t₁₁ after the period (1) elapses, the plasmatemperature decreases. At this timing, that is, at the timing t₁₁ whenthe HF power shifts to the Low power level lower than the High powerlevel, the LF2 power shifts to the ON state, and in the period (6) thatcoincides with the period (2) in time, the LF2 power is maintained inthe ON state. Accordingly, the amount of by-products during the etchingmay be suppressed, and the etching may be promoted.

The LF1 power is maintained in the OFF state in the period (5) thatcoincides with the period (2) in time from the timing t₁₁ to a timingt₁₂. In the present embodiment, at the timing t₁₂, the HF power shiftsto the OFF state, the LF1 power is maintained in the OFF state, and theLF2 power shifts to the OFF state. The HF power is maintained in the OFFstate in the delay time T_(delay). However, the power level of the HFpower in the delay time T_(delay) may be the Low level lower than thepower level of the HF power in the period (1). By further lowering thepower level of the HF power, it is possible to reduce the generation ofradicals and ions in the delay time T_(delay) before a timing t₂₂ whenthe LF1 power is supplied. At the timing t₂₂ after the delay timeT_(delay) elapses from the timing t₁₂, the LF1 power shifts to the ONstate. At the timing t₂₂, the HF power and the LF2 power are maintainedin the OFF state. As a result, the flux of ions that reach the bottom ofthe recess formed in the etching target film may be controlled in theperiod (4) from the timing t₂₂ to the timing t₁₃ after the delay timeT_(delay) elapses. At this time, the period (4) is set to time of 30 usor less. Further, the period (4) does not overlap with the period (1) intime. The period (5) that coincides with the period (2) in time, and theexhaust period are set to arbitrary times, and may be each longer than30 μs. That is, in the present example, the LF1 power is maintained inthe ON state for the time of 30 us or less in the period (4). In thisway, when the LF1 power is supplied for the short time of 30 us or lessin the period (4), the incidence angle of ions may be controlled to bemore vertical, so that an etching with a high anisotropy may beimplemented. However, when the delay time T_(delay) is excessively long,the ions are lost, and thus, the delay time T_(delay) is preset to anappropriate value.

FIG. 9 illustrates another example of the control of the radio-frequencypower pulses of the three frequencies. In this example as well, thecontrol of the pulsed signal of each of the HF power, the LF1 power, andthe LF2 power is repeated per cycle that includes the first pulse cycleof the HF power, the second pulse cycle of the LF1 power, and the thirdpulse cycle of the LF2 power. All of the pulse cycles may include theexhaust period.

The pulse cycle patterns of FIG. 9 and the pulse cycle patterns of FIGS.7 and 8 are different from each other, in that while the delay timeT_(delay) in FIGS. 7 and 8 is provided immediately before the LF1 powershifts to the ON state, the delay time T_(delay) in FIG. 9 is providedimmediately before the LF2 power shifts to the ON state.

In the present example, in the period (1), the HF power is maintained atthe High power level, and the LF1 power and the LF2 power are maintainedin the OFF state. In the periods (5) and (7) that coincide with theperiods (2) and (3) in time, all of the HF power, the LF1 power, and theLF2 power are maintained in the OFF state (the exhaust period).

Then, at a timing t₂₁, the HF power shifts to the Low power level lowerthan the High power level, and the LF1 power shifts to the ON state. Atthe timing t₂₁, the LF2 power is maintained in the OFF state. Then, inthe period (2), the HF power is maintained at the Low power level. TheLF1 power is maintained in the ON state in for time of 30 us or less inthe period (4) that overlaps with the period (2) in time (i.e., thatcoincides with a first portion of the period (2) in time). The LF1 powershifts to the OFF state at the timing t₂₂ in the period (2), and the LF2power shifts to the ON state at a timing t₂₃ after the delay timeT_(delay) elapses from the timing t₂₂. At the timings t₂₂ and t₂₃, theHF power is maintained at the Low power level. Then, the LF2 power ismaintained in the ON state in the period (6) that overlaps with theperiod (2) in time (i.e., that coincides with a second portion of theperiod (2) in time) from the timing t₂₃.

As described above, in the present example, the LF1 power and the LF2power are alternately turned ON in the period (2) when the HF power ismaintained at the Low power level. Further, in the period (4), the LF1power is supplied for the short time of 30 us or less. Accordingly, theincidence angle of ions may be controlled to be more vertical, so thatan etching with a high anisotropy may be implemented. Since the controlof the exhaust period from a timing t₂₄ to a timing t₂₅ after the period(6) elapses is the same as that of the other pulse cycles, descriptionsthereof will be omitted.

As described above, according to the plasma processing apparatus and theplasma processing method of the present embodiment, the performance of aprocess may be improved by using a plurality of radio-frequency powerpulsed signals.

According to an aspect, the performance of a process may be improved byusing a plurality of radio-frequency power pulsed signals.

From the foregoing, it will be appreciated that various embodiments ofthe present disclosure have been described herein for purposes ofillustration, and that various modifications may be made withoutdeparting from the scope and spirit of the present disclosure.Accordingly, the various embodiments disclosed herein are not intendedto be limiting, with the true scope and spirit being indicated by thefollowing claims.

What is claimed is:
 1. A plasma processing apparatus comprising: achamber; a first matching circuit coupled to the chamber; a secondmatching circuit coupled to the chamber; a first RF generator coupled tothe first matching circuit, and configured to generate a first RF pulsedsignal including a plurality of first pulse cycles, each first pulsecycle including a first period, a second period, and a third period, andthe first RF pulsed signal having a first power level in the firstperiod, a second power level in the second period, and a third powerlevel in the third period; a second RF generator coupled to the secondmatching circuit, and configured to generate a second RF pulsed signalincluding a plurality of second pulse cycles, each second pulse cycleincluding a fourth period and a fifth period, the second RF pulsedsignal having a frequency lower than a frequency of the first RF pulsedsignal and having a fourth power level in the fourth period and a fifthpower level in the fifth period, and the fourth period being set not tooverlap with the first period; and a third RF generator coupled to thesecond matching circuit, and configured to generate a third RF pulsedsignal including a plurality of third pulse cycles, each third pulsecycle including a sixth period and a seventh period, the third RF pulsedsignal having a frequency lower than the frequency of the second RFpulsed signal and having a sixth power level in the sixth period and aseventh power level in the seventh period, and the sixth period beingset not to overlap with the first period and the fourth period.
 2. Theplasma processing apparatus according to claim 1, wherein the thirdpower level, the fifth power level, and the seventh power level are zeropower levels.
 3. The plasma processing apparatus according to claim 2,wherein the first power level is larger than the second power level, thesecond power level is larger than the third power level, the fourthperiod overlaps with the third period, and the sixth period overlapswith the second period.
 4. The plasma processing apparatus according toclaim 3, wherein each of the plurality of first pulse cycles shifts fromthe first period to the third period, and shifts from the third periodto the second period, the fourth period coincides with the third period,and the sixth period coincides with the second period.
 5. The plasmaprocessing apparatus according to claim 3, wherein each of the pluralityof first pulse cycles shifts from the first period to the third period,and shifts from the third period to the second period, the fourth periodstarts after a delay time elapses since the shift from the first periodto the third period, and ends simultaneously with the shift from thethird period to the second period, and the sixth period coincides withthe second period.
 6. The plasma processing apparatus according to claim3, wherein each of the plurality of first pulse cycles shifts from thefirst period to the second period, and shifts from the second period tothe third period, the fourth period starts after a delay time elapsessince the shift from the second period to the third period, and endssimultaneously with an end of the third period, and the fifth periodcoincides with the second period.
 7. The plasma processing apparatusaccording to claim 2, wherein the first power level is larger than thesecond power level, the second power level is larger than the thirdpower level, the fourth period overlaps with the second period, and thesixth period overlaps with the third period.
 8. The plasma processingapparatus according to claim 7, wherein each of the plurality of firstpulse cycles shifts from the first period to the third period, andshifts from the third period to the second period, the fourth periodstarts simultaneously with the shift from the third period to the secondperiod, and ends before an end of the second period, and the sixthperiod starts simultaneously with an end of the fourth period or after adelay time elapses after the end of the fourth period, and ends beforethe end of the second period.
 9. The plasma processing apparatusaccording to claim 8, wherein each of the plurality of first pulsecycles is 50 μs to 1,000 μs.
 10. The plasma processing apparatusaccording to claim 9, wherein the first RF pulsed signal is a frequencyof 20 MHz to 60 MHz, the second RF pulsed signal is a frequency of 1 MHzto 15 MHz, and the third RF pulsed signal is a frequency of 100 kHz to 4MHz.
 11. The plasma processing apparatus according to claim 10, whereinthe third RF pulsed signal has a zero power level in a period when thesecond RF pulsed signal has a power level larger than zero.
 12. Theplasma processing apparatus according to claim 1, wherein the firstpower level is larger than the second power level, the second powerlevel is larger than the third power level, the fourth period overlapswith the third period, and the sixth period overlaps with the secondperiod.
 13. The plasma processing apparatus according to claim 1,wherein the first power level is larger than the second power level, thesecond power level is larger than the third power level, the fourthperiod overlaps with the second period, and the sixth period overlapswith the third period.
 14. The plasma processing apparatus according toclaim 1, wherein each of the plurality of first pulse cycles is 50 μs to1,000 μs.
 15. The plasma processing apparatus according to claim 1,wherein the first RF pulsed signal is a frequency of 20 MHz to 60 MHz,the second RF pulsed signal is a frequency of 1 MHz to 15 MHz, and thethird RF pulsed signal is a frequency of 100 kHz to 4 MHz.
 16. Theplasma processing apparatus according to claim 1, wherein the third RFpulsed signal has a zero power level in a period when the second RFpulsed signal has a power level larger than zero.
 17. A plasmaprocessing apparatus comprising: a chamber; at least one first matchingcircuit coupled to the chamber; a first RF generator coupled to the atleast one first matching circuit, and configured to generate a first RFpulsed signal including a plurality of first pulse cycles, each firstpulse cycle including a first period and a second period, and the firstRF pulsed signal having a first power level in the first period and asecond power level in the second period; and a second RF generatorcoupled to the at least one first matching circuit, and configured togenerate a second RF pulsed signal including a plurality of second pulsecycles, each the second pulse cycle including a third period and afourth period, the second RF pulsed signal having a frequency lower thana frequency of the first RF pulsed signal, and having a third powerlevel in the third period and a fourth power level in the fourth period,and the third period being set not to overlap with the first period,wherein the second power level and the fourth power level are zero powerlevels.